diff --git a/src/DETHRACE/common/utility.c b/src/DETHRACE/common/utility.c
index 9e28473a..9446fff7 100644
--- a/src/DETHRACE/common/utility.c
+++ b/src/DETHRACE/common/utility.c
@@ -26,16 +26,16 @@
 #define MIN_SERVICE_INTERVAL 200
 // <<
 
-int gIn_check_quit;
-tU32 gLost_time;
+int gIn_check_quit = 0;
+tU32 gLost_time = 0;
 #if BR_ENDIAN_BIG
-tU32 gLong_key[4] = { 0x6C1B995F, 0xB9CD5F13, 0xCB04200E, 0x5E1CA10E };
-tU32 gOther_long_key[4] = { 0x67A8D626, 0xB6DD451B, 0x327E2213, 0x15C29437};
+tU32 gLong_key[4] = { 0x6c1b995f, 0xb9cd5f13, 0xcb04200e, 0x5e1ca10e };
+tU32 gOther_long_key[4] = { 0x67a8d626, 0xb6dd451b, 0x327e2213, 0x15c29437};
 #else
-tU32 gLong_key[4] = { 0x5F991B6C, 0x135FCDB9, 0x0E2004CB, 0x0EA11C5E };
-tU32 gOther_long_key[4] = { 0x26D6A867, 0x1B45DDB6, 0x13227E32, 0x3794C215 };
+tU32 gLong_key[4] = { 0x5f991b6c, 0x135fcdb9, 0x0e2004cb, 0x0ea11c5e };
+tU32 gOther_long_key[4] = { 0x26d6a867, 0x1b45ddb6, 0x13227e32, 0x3794c215 };
 #endif
-int gEncryption_method;
+int gEncryption_method = 0;
 char* gMisc_strings[250];
 br_pixelmap* g16bit_palette;
 br_pixelmap* gSource_for_16bit_palette;
@@ -1168,31 +1168,34 @@ void DecodeLine2(char* pS) {
         }
         if (gEncryption_method == 1) {
             if (c == '\t') {
-                c = 0x80;
+                c = 0x9f;
             }
-            c -= 0x20;
-            if (!(c & 0x80)) {
-                c = (c ^ key[seed]) & 0x7f;
-                c += 0x20;
-            }
-            seed += 7;
-            seed = seed % 16;
 
-            if (c == 0x80) {
+            c -= 0x20;
+            c ^= key[seed];
+            c &= 0x7f;
+            c += 0x20;
+
+            seed += 7;
+            seed %= 16;
+
+            if (c == 0x9f) {
                 c = '\t';
             }
         } else {
             if (c == '\t') {
-                c = 0x9f;
+                c = 0x80;
             }
             c -= 0x20;
-            c = (c ^ key[seed]) & 0x7f;
+            if ((c & 0x80) == 0) {
+                c ^= key[seed] & 0x7f;
+            }
             c += 0x20;
 
             seed += 7;
-            seed = seed % 16;
+            seed %= 16;
 
-            if (c == 0x9f) {
+            if (c == 0x80) {
                 c = '\t';
             }
         }
diff --git a/test/DETHRACE/test_utility.c b/test/DETHRACE/test_utility.c
index 36c9642a..83451224 100644
--- a/test/DETHRACE/test_utility.c
+++ b/test/DETHRACE/test_utility.c
@@ -18,7 +18,7 @@ void test_utility_EncodeLinex() {
 
 void test_utility_DecodeLine2() {
     char buf[50];
-    gEncryption_method = 1;
+    gEncryption_method = 2;
     // first line of GENERAL.TXT, "@" prefix and line ending stripped
     char input[] = "\x29\x2a\x9c\x22\x61\x4d\x5e\x5f\x60\x34\x64\x57\x8d\x2b\x82\x7b\x33\x4c";
     strcpy(buf, input);
diff --git a/tools/decode_datatxt.py b/tools/decode_datatxt.py
index 6e597f6a..f81c83a7 100755
--- a/tools/decode_datatxt.py
+++ b/tools/decode_datatxt.py
@@ -13,43 +13,94 @@ OTHER_LONG_KEY = (
 )
 
 
+class Byte:
+    def __init__(self, v: int):
+        self.v = v & 0xff
+
+    def __add__(self, v: int):
+        return Byte(self.v + v)
+
+    def __iadd__(self, v: "Byte"):
+        self.v = (self.v + v) & 0xff
+        return self
+
+    def __sub__(self, v: int):
+        return Byte(self.v - v)
+
+    def __isub__(self, v: "Byte"):
+        self.v = (self.v - v) & 0xff
+        return self
+
+    def __mod__(self, v: int):
+        return Byte(self.v % v)
+
+    def __imod__(self, v: int):
+        self.v %= v
+        return self
+
+    def __xor__(self, v: int):
+        return Byte(self.v ^ v)
+
+    def __ixor__(self, v: int):
+        self.v = (self.v ^ v) & 0xff
+        return self
+
+    def __and__(self, v: int):
+        return Byte(self.v & v)
+
+    def __iand__(self, v: int):
+        self.v = (self.v & v) & 0xff
+        return self
+
+    def __eq__(self, other):
+        if isinstance(other, Byte):
+            return self.v == other.v
+        elif isinstance(other, int):
+            return self.v == (other & 0xff)
+        raise ValueError(f"Object {other:r} of invalid type {type(other)}")
+
+
 def decode_line(line: bytes, method: int) -> str:
     line = line.rstrip(b"\r\n")
     key = LONG_KEY
-    seed = len(line) % 16
+    seed = len(line) % len(LONG_KEY)
     dline = bytearray(len(line))
     for i, c in enumerate(line):
-        if i >= 2:
-            if line[i - 1] == b'/' and line[i - 2] == b'/':
-                key = OTHER_LONG_KEY
+        b = Byte(c)
+        if dline[i - 2:i] == b'//':
+            key = OTHER_LONG_KEY
         if method == 1:
-            if c == ord(b'\t'):
-                c = 0x80
-            c -= 0x20
-            if not (c & 0x80):
-                c ^= key[seed]
-                c &= 0x7f
-                c += 0x20
+            if b == ord(b'\t'):
+                b = Byte(0x9f)
+
+            b -= 0x20
+            b ^= key[seed]
+            b &= 0x7f
+            b += 0x20
 
             seed += 7
-            seed %= 16
-            if c == 0x80:
-                c = ord(b'\t')
+            seed %= len(key)
+
+            if b == 0x9f:
+                b = Byte(ord(b'\t'))
         else:
-            if c == ord(b'\t'):
-                c = 0x9f
-            c -= 0x20
-            c ^= key[seed]
-            c &= 0x7f
-            c += 0x20
+            if b == ord(b'\t'):
+                b = Byte(0x80)
+
+            b -= 0x20
+            if (b & 0x80) == 0:
+                b ^= key[seed] & 0x7f
+            b += 0x20
 
             seed += 7
-            seed %= 16
-            if c == 0x9f:
-                c = ord(b'\t')
-        dline[i] = c
+            seed %= len(key)
+
+            if b == 0x80:
+                b = Byte(ord(b'\t'))
+        dline[i] = b.v
     return dline.decode(errors="replace")
 
+
 def main():
     parser = argparse.ArgumentParser(allow_abbrev=False, description="Decode a Carmageddon encoded file")
     parser.add_argument("file", metavar="FILE", nargs="?", help="input file (default=stdin)")